1. Field of the Invention
The present invention relates to a side arm transfer device that transfers a load.
2. Description of the Related Art
An automated warehouse is provided with a stacker crane for moving a load onto and out of a shelf installed inside the automated warehouse. The stacker crane includes a travelling carriage, a lifting table liftably mounted on a mast provided on the travelling carriage, and a side arm transfer device provided on the lifting table (e.g., WO 2014/034173 A1).
The side arm transfer device is provided with a pair of arms, and hooks are provided on each of the arms. End portions of a load are hooked by the hooks and the arms are extended or retracted to push or pull the load, to transfer the load.
In such a side arm transfer device, when a load is to be transferred to the shelf, whether or not there is a load in a intended transfer location is previously detected (first-in item detection) and whether or not there is a space that each arm can enter is also previously detected (space detection).
However, in order to perform the first-in item detection and the space detection described above, separate photoelectric sensors are required to be used for the respective detection.
Thus, at the time of assembling the device, a plurality of photoelectric sensors are required to be assembled to the side arm transfer device, thus causing wiring arrangement, optical axis alignment, and the like, to take time, and the cost to increase. In particular, in the case of a side arm transfer device which is configured to be capable of simultaneously moving loads to two mounting locations on the front side and the rear side of the shelf, photoelectric sensors have been respectively required for performing the first-in item detection on the front side, the first-in item detection on the rear side, the space detection on the front-side arm, and the space detection on the rear-side arm. This has caused the number of photoelectric sensors to further increase and the assembly to take longer time.